Often applied in process automation technology are field devices, which serve for registering and/or influencing process variables. Thus, sensors, such as, for example, fill-level measuring devices, flow measuring devices, pressure- and temperature-measuring devices, pH-redox potential measuring devices, conductivity measuring devices, serve for registering corresponding process variables, fill-level, flow (e.g. flow rate), pressure, temperature, pH-value, and conductivity, respectively, while actuators, such as, for example, valves or pumps, serve for influencing process variables, such as, for example, changing the flow of a liquid in a section of pipeline, or the fill-level in a container. Referred to as field devices are, in principle, all devices placed near a process for delivering or processing process-relevant information. Besides sensors and actuators, also referred to as field devices are units, such as remote I/Os, gateways, linking devices, etc., connected directly to a fieldbus and serving for communication with superordinated units. A large number of such field devices are manufactured and sold by the firm, Endress+Hauser.
In modern industrial plants, field devices are, as a rule, connected via bus systems (Profibus®, Foundation® Fieldbus, HART®, etc.) with superordinated units. Normally, the superordinated units are control systems, or control units, such as, for example, a PLC (programmable logic controller). The superordinated units serve for, among other purposes, process control, process visualization, process monitoring, as well as for start-up of the field devices.
For servicing field devices, especially for parametering and configuring (these being referenced generically in the following as “parametering”) field devices and/or for readout of parameter values out of a field device, as a rule, a servicing program (operating tool—e.g. FieldCare® of Endress+Hauser) is provided in a superordinated unit. In the parametering, especially, parameters of the field device are set, or changed. The superordinated unit can, in such case, be connected directly to the fieldbus, to which the relevant field devices are connected, or to a superordinated communication network. Additionally, a field device can be serviced by a servicing unit, such as, for example, a portable personal computer (laptop), a portable, hand operating device (handheld), a PDA (Personal Digital Assistant), etc., in which a servicing program is implemented and which is connected to the fieldbus of the field device to be parametered.
In order to enable an accessing (e.g. a read access or a write access) of individual parameters of a field device, there are associated, at least with the parameters, which can be accessed via the fieldbus, in each case, fieldbus specific, parameter addresses. Depending on the kind of fieldbus used, in such case, a corresponding fieldbus-specific parameter addressing system is used. For example, in the bus system, Profibus®, an individual parameter is addressed by specifying its slot and index. The associating of slot and index to individual parameters is specified, for example, in the “Device Description” (DD) and/or in the “Device Type Manager” (DTM), so that it is available for a superordinated unit or a servicing device. This fieldbus-specific parameter addressing system is distinguished from the device internal parameter addressing system. Device-internally, the parameters are grouped in blocks (“BlockID”), depending on belonging, to individual function blocks (e.g. function blocks “Analog Input” (AI) and/or “Analog Output” (AO) (in the case of Profibus® and Foundation® Fieldbus), components (e.g. current supply, display, etc.), to a physical block, a transducer block, etc. Within the blocks, the parameters are distinguished device-internally by parameter identifications (ParameterID). The device-internal parameter addressing system, especially the association of the “BlockID” and the “ParameterID” to individual parameters, is determined, in such case, by the manufacturer of a field device.